The invention relates to a charge coupled device comprising a semiconductor body having a semiconductor layer of at least substantially one conductivity type situated at a surface, means to deplete the semiconductor layer over its whole thickness at least in the absence of a supply of majority charge carriers while avoiding breakdown, a row of electrodes provided on the surface of the body above the semiconductor layer and separated therefrom by a barrier junction and connected to voltage sources for applying clock voltages as a result of which potential wells for storing and transporting information-representing charge packets are generated in the interior of the semiconductor layer and separated from the surface, an input stage having a zone which constitutes a source of charge carriers and an input electrode situated between said zone and the said electrode regions and separated from the body by an insulating layer, by means of which electrode a potential well can be induced in the semiconductor layer, and an input signal source for supplying an input signal in the form of a voltage difference between the source of charge carriers and the input electrode which determines the size of a packet of charge carriers which flow from the source in the potential well below the input electrode.
Charge coupled devices with bulk transport are generally known and are often referred to in literature by the abbreviations bccd (buried channel charge coupled device) and pccd (peristaltic charge coupled device). These devices are distinguished in particular in that the transport of the charge packets can take place--at least substantially--not along the surface of the semiconductor body, but at some distance therefrom, in the interior of the semiconductor layer. As a result of this, the transport efficiency is not or at least substantially not influenced by surface states. Since furthermore the charge transport can take place under the influence of comparatively strong electric fields as a result of a comparatively large distance between the charge packets and the electrodes, devices of this type generally show a very high speed.
The zone which constitutes the source of charge carriers may be connected to the signal source via an ohmic connection. However, said zone may alternatively be kept at a fixed potential while the signal source is connected to the said input electrode, if desired via a clock voltage source.
For many applications it is desirable for the size of the charge packet to be formed below the input electrode to vary linearly or at least substantially linearly with the value of the input signal.
In charge coupled devices with bulk transport, potential wells are induced which are situated at a finite distance from the surface of the semiconductor body. When the size of the charge packet increases, the charge will be stored closer and closer to the surface and the associated electrode. As a result of this the capacity of the charge storage space is not constant but increases as the charge packet becomes larger so that a nonlinearity is introduced upon converting the input signal into charge packets.